1. Field of the Invention
The present invention relates to a polishing apparatus for polishing a workpiece such as a semiconductor wafer to a flat mirror finish, and more particularly to a polishing apparatus having a liquid leakage monitoring device.
2. Description of the Related Art
Recent rapid progress in semiconductor device integration demands smaller and smaller wiring patterns or interconnections and also narrower spaces between interconnections which connect active areas. One of the processes available for forming such interconnections is photolithography. Though the photolithographic process can form interconnections that are at most 0.5 xcexcm wide, it requires that surfaces on which pattern images are to be focused by a stepper be as flat as possible because the depth of focus of the optical system is relatively small.
It is therefore necessary to make the surfaces of semiconductor wafers flat for photolithography. One customary way of flattening the surfaces of semiconductor wafers is to polish them with a polishing apparatus, and such a process is called Chemical Mechanical polishing.
Conventionally, a polishing apparatus has a polishing section having a turntable and a top ring which rotate at respective individual speeds. A polishing cloth is attached to the upper surface of the turntable. A semiconductor wafer to be polished is placed on the polishing cloth and clamped between the top ring and the turntable. An abrasive liquid containing abrasive grains is supplied onto the polishing cloth and retained on the polishing cloth. During operation, the top ring exerts a certain pressure on the turntable, and the surface of the semiconductor wafer held against the polishing cloth is therefore polished by a combination of chemical polishing and mechanical polishing to a flat mirror finish while the top ring and the turntable are rotated.
After, for example, one or more semiconductor wafers have been polished, the polishing cloth is processed to recover its original polishing capability. Various processes have been and are being developed for restoring the polishing cloth, and are collectively called xe2x80x9cdressingxe2x80x9d. The polishing cloth is dressed by a dressing tool installed in the polishing apparatus in order to enable the polishing apparatus to perform a good polishing function at all times without undesired degradation of a polishing performance.
Some polishing apparatuses incorporate a cleaning section for conveying semiconductor wafers and cleaning the semiconductor wafers. The cleaning section comprises a workpiece conveying robot for taking a semiconductor wafer out of a cassette and delivering the semiconductor wafer to the polishing section having the turntable and the top ring, a cleaning device for cleaning the semiconductor wafer which has been polished, and a drying device for drying the semiconductor wafer which has been cleaned.
The polishing apparatus further comprises an abrasive liquid supply device which supplies abrasive liquid to the polishing section, and a cooling water supply device which supplies cooling water to the polishing section and the like.
The polishing section, the cleaning section, the abrasive liquid supply device, and the cooling water supply device are in danger of a liquid leakage due to an unexpected failure of some internal devices thereof because they use various liquids or hold various liquids therein. Therefore, it is desirable that when liquid leakage occurs in the above sections and devices i.e. the occurrence, of such leakage being a predetermined malfunction such liquid leakage is quickly detected and stopped.
It is therefore an object of the present invention to provide a polishing apparatus which can quickly detect a liquid leakage and stop it without operator intervention.
According to one aspect of the present invention, there is provided a polishing apparatus for polishing a surface of a workpiece comprising: a polishing section for polishing a surface of a workpiece; a cleaning section for cleaning the workpiece which has been polished; a first liquid leakage sensor provided in said polishing section for detecting a liquid leakage which occurs in said polishing section; a second liquid leakage sensor provided in said cleaning section for detecting a liquid leakage which occurs in said cleaning section; and a controlling device for stopping the supply of liquid to said polishing section or said cleaning section in which said liquid leakage occurs when either one of said first and second liquid leakage sensors detects said liquid leakage.
According to another aspect of the present invention, there is provided a polishing apparatus for polishing a surface of a workpiece comprising: a polishing section for polishing a surface of a workpiece; a cleaning section for cleaning the workpiece which has been polished; an abrasive liquid supply device for supplying abrasive liquid to a polishing surface in the polishing section; a temperature adjusting device for adjusting temperature of liquid which is supplied to at least one of the polishing section, the cleaning section and the abrasive liquid supply device; a plurality of liquid leakage sensors provided respectively in the polishing section, the cleaning section, the abrasive liquid supply device and the temperature adjusting device for detecting a liquid leakage which occurs in the polishing section, the cleaning section, the abrasive liquid supply device and the temperature adjusting device; a liquid supply stop device for stopping the supply of liquid to the polishing section, the cleaning section, the abrasive liquid supply device and the temperature adjusting device; and a controlling device for stopping the supply of liquid to the polishing section, the cleaning section, the abrasive liquid supply device, or the temperature adjusting device in which the liquid leakage occurs when at least one of the liquid leakage sensors detects the liquid leakage.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate a preferred embodiment of the present invention by way of example.